The present invention relates to a new and improved apparatus for sequentially loading a plurality of layers of bundles of newspapers onto a pallet.
A known apparatus for sequentially loading layers of bundles of newspapers onto a pallet is disclosed in U.S. patent application Ser. No. 335,839 filed Dec. 30, 1981, U.S. Pat. No. 4,439,084, by James S. Werkheiser and entitled "Palletizer for Newspaper Bundles". The apparatus disclosed in this application includes a conveyor which sequentially moves bundles to a row staging area. A row sweep moves a row of bundles from the row staging area to a layer staging area. When a layer of bundles has been accumulated at the layer staging area, a layer sweep moves the layer of bundles onto a retractable floor. The retractable floor then opens and the bundles are dropped onto a pallet disposed on an elevator immediately beneath the floor. The elevator is then lowered so that the floor can close to receive a next succeeding layer of bundles.
During operation of the known apparatus disclosed in the aforementioned Werkheiser application, it is necessary to detect when the elevator has lowered the pallet through a sufficient distance so that the uppermost layer of bundles on the pallet is just beneath the floor. To this end, a light source and photocell are positioned on opposite sides of the elevator at a location immediately beneath the floor. When the layer of bundles is dropped onto the pallet, the light beam is blocked. When the elevator has lowered the bundles to the desired level beneath the floor, the light beam just clears the layer of bundles and activates the photocell to provide a signal to a control the apparatus for the palletizer.
Although the apparatus disclosed in the aforementioned Werkheiser application is generally satisfactory in its operation, difficulty has been encountered due to false indications of the level of the top layer of bundles. The false indications of the position of the top layers of the bundles were due to sheets of paper projecting upwardly from the layer of bundles and/or one of the bundles being tilted or extending upwardly further than the other bundles in the layer. The upwardly projecting pieces of paper may block the light beam so that the elevator lowers the bundles further than necessary. If a bundle is offset to one side of the light beam and extends upwardly from the other bundles in the layer, the upwardly projecting bundle may extend into the opening in the floor even though the remainder of the bundles in the layer are clear of the opening.